What cartridge am I missing?

Trying to figure out what cartridge I should build or be looking for next. Here is a list of what ones I currently have, all factory unless other wise noted. I know I have a caliber to kill almost anything but wondering if there's that magic one I'm missing.

A magnum 30 is an absolute must in any collection.
300WSM
300Win
300Wby
300RUM
All are great choices. & all can fit the bill for most any situation in N. America.
A 338Win, or a 375 of some kind would be tied for my # 2 choice with the cartridges you already own.